Personally, for basic PPL teaching I like PP and have all my briefs on laptop, I find that just whiteboard I waste far to much time writing stuff that I can have pre prepared, having said that, you DO need to have a white board/paper and pen available and be ready to go off brief if needed.
Most of my instructing though tends to be with people that have already got a PPL and I am bringing out points that I cannot really pre prepare for so a white board or paper and pen are better.